An EEG is a painless test to record the electrical activity in your brain and help pinpoint the source of symptoms like seizures or memory loss. 

The EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG. Depending on the lesion’s size and location, people with brain lesions, prolonged tumors, or strokes may have prolonged EEG waves.

The test diagnoses other disorders that influence brain activity, such as Alzheimer’s disease, certain psychoses, and a sleep disorder called narcolepsy. The EEG is used to determine the overall electrical activity of the brain. The EEG is used to monitor blood flow in the brain during surgical procedures.